Conventional ultrasound imaging systems typically include a hand-held probe coupled by cables to a large rack-mounted console processing and display unit. The probe typically includes an array of ultrasonic transducers which transmit ultrasonic energy into a region being examined and receive reflected ultrasonic energy returning from the region. The transducers convert the received ultrasonic energy into low-level electrical signals which are transferred over the cable to the processing unit. The processing unit applies appropriate beam forming techniques to combine the signals from the transducers to generate an image of the region of interest.
Typical conventional ultrasound systems include a transducer array each transducer being associated with its own processing circuitry located in the console processing unit. The processing circuitry typically includes driver circuits which, in the transmit mode, send precisely timed drive pulses to the transducer to initiate transmission of the ultrasonic signal. These transmit timing pulses are forwarded from the console processing unit along the cable to the scan head. In the receive mode, beamforming circuits of the processing circuitry introduce the appropriate delay into each low-level electrical signal from the transducers to dynamically focus the signals such that an accurate image can subsequently be generated.
Because all of the circuitry is located remote from the probe, rather bulky cables tether the probe to the console processing unit. Typically, separate cables provide power and control signals to the probe head. Those cables administer a significant torque onto the probe head. To drive 128 transducers, at least 128 transmit/receive lines (one for each transducer) are typically required. As a result, the ultrasound operator must fight that cable torque to position and operate the probe head.
In accordance with a preferred embodiment of the invention, further improvements in portable ultrasound medical imaging systems developed for use with personal computers are provided. In one embodiment the control circuitry and beamforming circuitry are localized in a hand-held probe. Such an integrated package simplifies the cable requirements of the probe, without adding significant weight to the probe.
An embodiment of the invention includes a probe having a plurality of circuit boards or circuit panels that are mounted within a generally rectangular cavity within a hand-held housing. The circuit panels each have one or more integrated circuits and are mounted in planes that are parallel to one another. These integrated circuits can be fabricated using a standard CMOS process that will support voltage levels between 5V and 200V.
A particular embodiment of the invention utilizes two or three circuit boards or panels, a center panel having a center system controller and a communication link to an external processor. The center panel can be mounted between a pair of surrounding panels, each including a memory and a beamforming circuit. The system accommodates the use of different probe elements and can employ a variable power supply that is adjusted to different levels for different probes. Also, it is desirable to use a variable clock generator so that different frequencies can be selected for different probes.
Another preferred embodiment of the invention provides a small probe that is connected by a first cable to an interface housing. The interface housing can contain the beamformer device and associated circuits and is a small light weight unit that can be held in one hand by the user while the other hand manipulates the probe. Alternatively, the interface housing can be worn on the body of the user with a strap, on the forearm or the waist with a belt, for example, or in a pocket of the user. A preferred embodiment using such an interface can include two or three circuit boards as described in greater detail herein.
In another preferred embodiment, the probe incorporating the beamformer, or the probe with the interface housing can be connected to a wearable personal computer. In this embodiment, the computer performing scan conversion, post signal processing or color doppler processing is located in a housing worn by the user, such as on the forearm, on the waist or in a pocket. A power supply board can be inserted into the probe, into the interface housing or in another external pod and can include a DC-DC converter. The display system can also include a head mounted display. A handheld controller can be connected to the computer or interface by wire or wireless connection.
A preferred embodiment of the invention can utilize certain safety features including circuits that check the power supply voltage level, that test every channel of the beamformer and assists in setting gain levels, that counts pulses per second and automatically shuts off the system to prevent over-radiating of the patient.
Another preferred embodiment of the invention employs the use of dedicated controls that the user can employ to perform specific tasks during a patient study. These controls are readily accessible and intuitive in use. These controls provide for freezing or unfreezing of the image on the display, for recording an image in electronic memory, to measure distances in two dimensions using a marker or caliper and a xe2x80x9csetxe2x80x9d function to fix two markers or calipers on screen, a track ball, touchpad or other manually manipulated element to control the marker, a time gain compensation control, such as 8 slide pots, to correct for sound attenuation in the body, scale or depth control to provide a zoom feature and for selection of focal zones.
The system can be employed with a number of probe system and imaging methods. These include the generation of color Doppler, power Doppler and spectral density studies. These studies can be aided by the use of contrast agents that are introduced into the body during a study to enhance the response to ultrasound signals. Such agents can also include medications that are acoustically released into the body when they are activated by specific acoustic signals generated by the probe transduce array.